Yes.
It's not a secret. Microsoft has said that .Net Framework is basically in maintenance mode and "will move slower". They are moving EF6, Winforms, and WPF to .Net Core (Windows only).
https://blogs.msdn.microsoft.com/dotnet/2018/10/04/update-on...
I've been developing on top of Microsoft environments for over 20 years and .Net is by far my favorite language. But, the writing is on the wall. Anyone who wants a long term career in development needs to run away from Windows as fast as possible and slowly move away from focusing exclusively on .Net.
Linux even dominates on Azure.
https://www.zdnet.com/article/linux-now-dominates-azure/
Microsoft knows that Windows can't compete in the cloud and selling Windows for desktops is not the future.